Passages have been traditionally secured by the use of doors affixed with a lock that permits entry by authorized users. Locks are mostly mechanical devices that can be opened by inserting a key into the lock lock's keyway and rotating the key. This requires the user to first locate and acquire the key and then perform a mechanical action in order to gain entry.
More recently, various types of keyless entry systems have been used to simplify entry by authorized users. There are generally two types of keyless entry systems—a non-passive keyless entry system and a passive keyless entry system. A non-passive keyless entry system comprises a base station and a portable data carrier configured to allow access to unlock a secured door, but such access requires the user to perform an authenticating action such as pressing a button on a key fob, swiping a key card through a card reader or positioning a smart card, chip card or data token in close proximity to and practically touching a proximity reader in order to gain entry.
For instance, one type of non-passive keyless entry system, such as a Remote Keyless Entry (RKE) system, is commonly deployed in automobiles for vehicular door locking and unlocking without inserting the car key into the vehicle's door lock. In the RKE system, a user must first locate and acquire the key fob and has to press a button on the key fob in order to open the car door or to unlock the vehicle's trunk.
A more recent evolution for vehicular entry has been the deployment of a Passive Keyless Entry (PKE) system. The vehicular PKE system also comprises a base station and a portable data carrier (e.g., a key fob) configured to allow access to unlock a secured vehicular opening, but such access does not require the user to perform an active authenticating action. Rather, entry can be gained when a user carrying a key fob approaches the vehicle where the vehicle's LF emitting antennas, positioned external to the vehicle's chassis where RF communication shielding is not a problem, detect the key fob.
The placement of the vehicular LF emitting antennas situated external to a tamper-resistant chassis is unsuitable for many non-vehicular secured access applications. Another disadvantage of the vehicular RKE and PKE systems is that the vehicular door locks and the electronic circuitries inside the vehicle that control the vehicular locking and unlocking functions are powered by the car's battery. Upon a complete discharge of the vehicle's battery, the car owner will no longer be able to gain entry to the vehicle or access its contents. Vehicular batteries are not ubiquitous, and thus, most people will not have a spare and fully charged car battery lying around. Obtaining and installing a suitably rated car battery for a particular make and model of a vehicle, especially after business hours, can be a real challenge.
Another disadvantage of the vehicular RKE and PKE systems is that the authorizing access codes of these vehicular systems are set by the vehicle manufacturers, where each key fob is paired with a specific vehicle and no one key fob will operate any vehicle other than the paired vehicle. A husband and wife couple having two different cars will each have to carry two different key fobs in order to access the two vehicles. The more vehicles one family has the more key fobs a family member has to use in order to access the vehicles. While this unique key fob to vehicle pairing provides a certain level of vehicular security, it is inconvenient for users having multiple vehicles, perhaps stored at different locations, to have to carry multiple key fobs and to fumble through several different key fobs to realize the matching key fob for the intended vehicle.
Another disadvantage of the vehicular RKE and PKE systems and other premise base entry systems such as garage door opening systems that rely on hopping or rolling codes, the base station of these systems using an encoder generates a new code each time when transmitting an access code. The portable data carrier after receiving the access code uses the same encoder to generate a new code that will be accepted by the base station in the future. Though the use of hopping or rolling codes prevents perpetrators from scanning and recording the access code and replaying it to open the door, there is a probability that the open button on the portable data carrier can be pressed inadvertently or accidentally while the portable data carrier is not in the transmission and reception range of the base station. This creates the possibility of desynchronizing the access code, even if the portable data carrier generates look-a-head codes ahead of time, there remains the possibility that the number of inadvertent or accidental pushes of the open button of the portable data carrier exceeds the number of look-a-head codes generated and the user would then be prevented from access.
Further, even if a user becomes aware that such a vehicular RKE and PKE systems or other premise base entry systems such as garage door opening systems has been compromised, there are no immediate steps that the user can take to rectify the security breach other than having the security system reprogrammed by the system's administrator or manufacturer. Technicians and dealers allowed to handle the reprogramming of these systems usually require the use of special tools generally not available to users of these systems to reprogram their key fobs; depending on the make and model of the vehicle or the premise base system, the cost of replacing a missing or stolen key fob and the reprogramming of the security system could amount to hundreds of dollars.
Aside from the replacement and the reprogramming expenditures, there is the inconvenience of contacting and waiting for the manufacturer or the dealer to have the key fob and the security system reprogrammed. The vehicular RKE systems and systems such as garage door opening systems also require the user to press a button on the key fob or the portable data carrier, and therefore, do not offer the benefit of the passive keyless entry system where no active authenticating actions are required in order to gain entry.
Another disadvantage of the vehicular RKE and PKE systems and similar non-vehicular access control systems that use portable data carriers similar to a key fob is that the door unlock button on the key fob can be depressed inadvertently or unintentionally and without the user's knowledge triggering the unlocking of the vehicle or the premise door; this unintended and unaware unlocking of the vehicle or the premise door can post security threats to person and property.
Another disadvantage of the vehicular RKE and PKE system and similar non-vehicular access control systems is that the panic button on the key fob can also be depressed inadvertently triggering an undesired alarm siren causing anxiety to the user and unwanted disturbance and annoyance to neighbors. False alarms caused by the inadvertent pressing of buttons on the key fob also results in additional drain on the key fob battery and the base station battery and can reduce the system's effectiveness prematurely.
Other than the vehicular RKE and PKE systems, there is a variety of premise-based keyless entry systems. There are systems that use infrared as a wireless communication medium between the base station and the portable data carrier. However, even though such systems do not require the inserting of a key into a door lock's keyway, these systems still require the user to physically locate and acquire the portable data carrier from the user's person or from the user's belonging; the user also has to point the portable data carrier's infrared beam at the base station's infrared reception sensor. The infrared beams used in such systems are very directional. They travel in straight lines and can be reflected or blocked, and like the pointing of a TV remote control, the user has to point the infrared beam pretty much directly at the base station's infrared sensor. The infrared transmission and reception can also be made less effective if the portable data carrier's infrared transmitter aperture or the base station's infrared reception sensor is soiled with dirt or other contaminants. The inconvenience of using IR base keyless entry systems where the user must first locate, acquire and press a button on the infrared transmitter prior to unlocking will be more apparent when the systems are used in the dark, in bad weather, when the user's hands are occupied with carrying groceries and belongings or when the user is holding an infant or a young child.
There are premise-based keyless entry systems that use ultrasound instead of infrared as a wireless communication medium between the base station and the portable data carrier. These systems also have the same disadvantage of requiring the user to physically locate and acquire the portable data carrier from the user's person or from the user's belonging. Furthermore, the user has to press a button on the ultrasound transmitter in order to achieve any unlocking. The inconvenience of using such ultrasound-based systems is similarly apparent when these systems are used in the dark, in poor weather, when the user's hands are occupied with holding a mobile phone or carrying things or when the user is carrying an infant or holding a baby.
There are other keyless premise entry systems that use key cards, smart cards, chip cards, tokens, or key fobs in conjunction with card readers or proximity readers. There are disadvantages in these systems as well. These systems generally are not passive keyless entry systems and their proximity detection ranges are generally very limited, usually no more than 20 to 30 millimeters (mm). Again, the mode of entry of these systems is not truly passive; rather, these systems will require a user to physically locate and acquire the portable data carrier (e.g., a key card, smart card, chip card, token or key fob) from the user's person or belonging, thereafter, the user is required to perform an authentication action such as swiping the key card through a card reader or position the smart card, chip card, token or key fob in close proximity to and practically touching the proximity reader in order to gain access.
There are RFID systems that provide keyless entry but the mode of entry is also not passive keyless. Again, a user is required to locate and acquire the portable data carrier and position the portable data carrier in very close proximity to and practically touching a proximity reader in order to gain entry.
There are RFID systems that are outdoors such as toll road systems and gate systems that are passive and have much greater RFID detection ranges. However, the dimensions of these systems are much larger compared to a typical keyless premise entry system because these systems require a larger or a multiple number of RF emitting antennas in order to achieve the greater detection distances. Also, these systems and other keyless access control systems aforementioned generally are powered externally and will require professional wiring and installation. The cost of labor and material in installing and maintaining these systems is another disadvantage.
There are also biometric entry systems that use fingerprints, palm prints, face recognition, voice recognition and iris scanning for access control and authentication. These systems require the enrollment of all of the users' credentials and have to acquire all the necessary biometric data prior to authentication. Similar to other non-passive keyless entry system, biometric entry systems are also non-passive entry systems and generally all biometric entry systems will require a user to perform an authenticating action before access can be granted. There are also additional disadvantages of the biometric entry systems, replacing biometric credentials is much more laborious and difficult if not impossible. If someone's face is compromised from a database, the compromised face credential cannot be replaced with a different face to authenticate the same person in granting access. A user wearing gloves in cold climate areas will have to remove the glove in order to use a fingerprint-based biometric entry system. The collection of biometric data will require the physical presence of every individual seeking access, there will be no guest entry possible if such a guest was not previously enrolled in the biometric system. The biometric recognition can also be made less effective if the biometric data acquiring device's surface or sensor is soiled with dirt or other contaminants or smudged with fingerprints from unclean hands or from hands with greasy lotions. Snow and rain can also obfuscate the detection surface and can make authentication less accurate or less effective. Further, biometric data acquisition and measurement equipment are expensive compared to other types of keyless entry systems. Finally, the ultimate disadvantage of such biometric systems is one of circumvention and personal safety. When criminals cannot get access to secured properties, there is a chance that the villains will stalk and assault the premise owner to gain access. If the premise is secured with a biometric system, the damage to the owner could be irreversible and potentially cost more than the secured property.
In summary, infrared, ultrasound, biometric and RFID systems as well as other premise-based systems that use key cards, smart cards, chip cards, tokens, or key fobs are all non-passive systems. These systems generally require a user to physically locate and acquire a portable authentication device from the user's person or belonging and to perform an authenticating action in order to gain entry. Thus, the convenience provided by such systems versus a conventional key and lock arrangement is not substantially improved.
Achieving a PKE proximity detection distance within a prescribed range (e.g., one-half meter to approximately one meter) and overcoming RF transmission and reception shielding effects that would be caused by encasing RF transmission and reception elements within a tamper resistant but ferromagnetic or electromagnetic RF shielding material has been the key challenges in developing a premise-based PKE system.
More specifically, the current flowing into a low frequency (LF) emitting antenna coil used in a PKE system radiates a near-field magnetic field that falls off with 1/r3 where “r” is the distance from the center of the LF emitting antenna coil. The magnetic field strength or the magnetic flux density from the magnetic field generated is therefore inversely proportional to the cube of the distance and decays with 1/r3. Thus, the effective proximity detection distance between the base station and the remote transponder in a PKE system will correspondingly decline in an exponential fashion as the distance between the base station and the remote transponder increases.
In addition, the transmission and the reception of RF signals, a form of electromagnetic radiation, by an antenna encased inside a ferromagnetic or conductive cage can be greatly attenuated or even completely blocked by the cage itself evidenced by the Faraday's cage effect. The main culprit in the reduction in the proximity detection distance of a PKE system lies with the Faraday's cage effect where the Faraday's cage shields the interior of a conductive casing from outgoing and incoming electromagnetic radiation if the conductive casing is thick enough and any holes of the casing are significantly smaller than the radiation's wavelength.
In the vehicular PKE systems, the LF emitting antennas are usually housed inside the exterior vehicular door handles or in areas of the vehicle where electromagnetic shielding is not a problem. In a premise-based PKE system, the Faraday's cage effect of electromagnetic shielding will become apparent and difficult to overcome when the RF communication elements of the PKE system such as the LF emitting antenna and the UHF receiver are housed in enclosures constituted with tamper resistant but electromagnetic interfering or shielding material. Furthermore, any conversions of the mechanism supplying power to such systems, such as the substitution of an alternating current (AC) power supply by a direct current (DC) power supply, and the miniaturization of the LF emitting and receiving antennas would further reduce the effective proximity detection distances of any PKE systems.
Evidently, implementing a passive keyless entry system where the LF emitting antenna and the UHF receiver have to be housed within ferromagnetic or electromagnetic RF shielding material, because of material strength required for maintaining system integrity, becomes problematic and presents a formidable challenge.